The invention relates to a linkage arrangement for moving members together or apart in a substantially linear motion without a substantial shift in a direction perpendicular to the desired linear motion. Typical linkages that are commonly used for a variety of purposes involve a pair of parallel members attached pivotally to a pair of parallel linkage members to form a parallelogram. If one of the parallel members is fixed, then motion of the parallelogram linkage results in an angular motionxe2x80x94in or out and up or down rather than simply in or out. The present invention relates to a linkage arrangement of the xe2x80x9cXxe2x80x9d or scissors type for moving members relative to one another in a substantially linear motion.
The invention disclosed herein is particularly useful as a control mechanism for expandable rooms in habitable structures, especially room structures that are telescopically slideable between retracted and extended positions for motorized or towed vehicles. A variety of recreational vehicles are known and used that have a room or a room portion that may be moved from a retracted position while the vehicle is moving over the road to an extended position when the vehicle is stationary in order to provide additional internal space. This type of an arrangement provides adequate space to accommodate users when a recreational vehicle is parked for habitation while still keeping the vehicle within governmental regulations that impose width limitations for vehicles on roads and highways. When these vehicles are stationary, they are frequently used for habitation for extended periods of time, and when so used, it is highly desirable to be able to maximize the available living space. This is done in a variety of ways in which the user can move a xe2x80x9cnestedxe2x80x9d portion of the expandable room out to its extended or expanded position, typically under hydraulic or electrical power.
These expandable room portions usually comprise a structure that includes a floor, a roof, an external end wall (typically generally parallel to the vehicle side wall), an open (or openable), interior end wall, and one or more side walls (typically generally perpendicular to the vehicle side wall). These components are typically made of frame members and wall panels. In the retracted position, the roof, floor and side walls are typically concealed from exterior view and the room exterior end wall forms a portion of the vehicle side wall. A large factor in the purchase of a vehicle of this type is the amount of useable space that is available inside the vehicle. Thus, it is desirable that the mechanism for extending and retracting the room take up a minimum of space.
The prior art for expanding and retracting expandable rooms generally employs hydraulic arms that are housed inside the vehicle or under the floor of the vehicle. The hydraulic arms contained within the vehicle require a housing unit when they are in their retracted position. This housing unit remains intact when the room is extended taking up space within the vehicle. The hydraulic arms that are housed under the floor are generally complex, relatively expensive, and may be unduly heavy. Further, when the room is in the retracted position, otherwise available storage space under the floor is lost. The additional weight also adversely affects the fuel economy of the vehicle. With the highly competitive market in these recreational vehicles, not only weight and space but also cost and reliability of operation are important factors.
Examples of improved types of linkage utilized in these expandable rooms are disclosed in co-pending patent applications Ser. No. 09/628874 filed Oct. 26, 2001 and entitled xe2x80x9cStraight Motion Parallelogram Linkagexe2x80x9d, and Ser. No. 10/065509 filed Oct. 25, 2002 and entitled xe2x80x9cLinkage for Expandable Roomsxe2x80x9d. It is the object of this invention to provide another type of mechanism for expanding rooms for vehicles which mechanism is reliable in use, lightweight, has fewer components and which will allow for maximum space inside the vehicle. It is a further object to provide a scissor type linkage that provides for motion of structural members together or away from one another in a substantially linear path without substantial movement of the members in a direction perpendicular to said path. It is a further object to provide a mechanism for the expansion and retraction of expandable rooms or structures when the rooms or structures are not designed for convenient housing of the mechanism in the floor. Finally, it is an object of the present invention to provide a mechanism wherein a force assist means such as, for example, a hydraulic cylinder, electric drive, or pneumatic control system can be used to drive the movement of a push-pull chain that in turn moves an expandable room, and if needed, such a chain can be provided on both sides of the room and synchronized.
The present invention includes a push-pull drive chain mechanism that can be powered by a hydraulic cylinder, electric drive or pneumatic or other similar control system, to affect the coordinated linear movement of an expandable room in a recreational vehicle. The drive chain moves generally vertically along a first structural member, such as a vehicle frame member, as the hydraulic cylinder extends or retracts to move the expandable room relative to the vehicle frame. The drive chain is pivotally connected at the proper place on the structural members, and in a preferred embodiment the chain is connected to one link of a scissors-type linkage assembly, the links that form the scissors extending and crossing between points of pivotal attachment with a structural member of the vehicle body and a second structural member of the expandable room. The drive chain is constructed and guided to provide the required force for opening and closing the scissors assembly.
There may be a scissors linkage assembly and drive chain mechanism on each side of the expandable room, each linkage assembly having a first link attached at one end to a vehicle frame member and at its other end to a structural member of the expandable room. The other link of the scissors linkage assembly is pivotally attached at one end to the vehicle frame member and at the other end to a structural member of the expandable room, the links crossing and being pivotally connected midway between their ends. The drive chain mechanism for each of the linkage assemblies is then attached to one of the links to expand or collapse the assembly and cause the expandable room to extend or retract. Use of two linkage assemblies, one on each side of the expandable room, improves the mechanical advantage in moving the expandable room inwardly and outwardly. Preferably, a torsion bar interconnects the linkage assemblies to equalize the pressures on the assemblies and thereby assure smooth, synchronized operation.